Tuning fork



TUNING FORK Filed June 18, 1925 N EBS Patented May 2s, 192,9..

UNITED STA l v BARON H. H-LGLUND, OF BROOKLYN, XNEW SSIGNOR TQ THEWESTERN UNION 'rias PATENT OFFICE.

marmara oonrm, orNnw Your, N; Y., a oonromrroncr Nrw You J TUNING ronx.-i

Application med June 18, 1925. Serial No. 58,118;

This invention pertains to the construction of tuning forks which aremore especially intended to act as governors for controlling the speedof motors and nchronously o eratin devices or as relays or repeating "ieectrica impulses in telegraph', 'telephone radio, photo-telegraphy,where uniformity o speed is essential. x An example of tuning forks dfthis type is found in U. S. patent to Houghtaling, No. 1,466,623 datedAugust 28, 1923.

Tuning forks intended for the above mentioned pur ses are constructedwith great precision rom steels of the best quality. Nevertheless, eventhe best of such prior tuning forks are subject to variations infrequency, at dilferent temperatures. These changes in frequency arecaused by a change in the elasticity of the fork, and by the actual chane in size due to expansion or contraction o the fork, orboth. v

After an extended research to develop means for overcoming thisdiiiiculty I have found that while the majority of steels, and othermetals that may be used\in the manufacture of forks of this kind, have anegative temperature coefficient of modulus of elasticity, certainmaterials may be obtained for which this coeiiicient is positive. Asteel possessing this positivefcoeicient whichA I have used iscomposed'of 36% nickel and havf ing a carbon content of .18 and iscommonly known as Invar steel but it is to be understood that myinvention is not limited to the use of this material. I l

The low carbon steels commonly known as machine steels? which have acarbon content 4wherein the coefficient of expansion and elasticity ofthe different materials combine in such a manner that the temperaturecoeiiicient of the fork as a whole becomes zero. I have further foundthat by the same means, the total temperature coeiiicient for the forkas IFa whole may be made any desired value with'- intended to be'coveedby my clans.

positive coelicient of ex in rthe two limits produced when the fork ismade of either one of the said materials above. The accompanymg drawingillustrates in conventlonal form a tuning fork constructed 1n accordancewith my invention.

I prefer to construct the outer portions '1,

ofthe (tines of nickel alloy steel and the inner portions 2 and yoke ofmachine steel, these parts being welded together, the line of the weldbeing indicated at '3. The yoke may be provided as usual with anextensionv or stem 4, by which it is supported upon a pillar in thesynchronizing controlling apparatus, relay or other well-known apparatusin which such tuning forksA are used. The proper proportions of nickelsteel and machine steel will vary with the different sizes of forksemployed. In forks constructed for use in controlling the speed ofrotary distrib- 'utors used in multiplex telegraph systems, I haveconstructed a fork in accordance with the invention disclosed herein inwhich the outer portions of the fork tines are eleven and one-tenthinches in length, made of said nickel steel, and the inner ends of thetines to the `this fork having a zero temperature eiect when the fork isused in the re lar manner and fully equipped. with s li ing weights asushown. in the Houghtaling Patent No. 1,466,623 previously referred to.

I have illustrated a tuning fork having two tines but it is evident thatmy invention is also applicable to vibratory reedshaving a single tineor member and hence they are I cla-im 1. The method of constructing atuning j fork which consists in combining with a bar of steel having anegative temperature coeicient of modulus of elasticity, a bar of steelhaving a positive temperature coeliicient of modulus of elasticity andwelding the ad'a-A cent ends to form an integral bar, where y thevibrations of the resulting integral bar are substantially unaffected bychanges in atmospheric temperature. I

2. A tuning fork having a vibratory member comprising a portion havingarpositive temperature coeliicient of modulus of elasticity and anotherportion having a negative temperature coeliicient of modulus ofelastic-` ity, the portionsbeing welded at their adjacent ends and beingso proportioned that the i vibratory member is substantially unaffectedby changes in atmospheric' temperature.

3. ftuning fork having a vibratory mem-- ber comprising a ortion' ofnickel alloy. steel 5 and a portion o Ymachine steel integrally unitedat 'their adjacent ends, said portions being so proportioned that thevibration `of said member is substantially unaffected by changesinatmospheric temperature. 10- 4. The method of making a tuning fork,which consists in forming each vibratory member of a plurality-of metalelements or' lengths welded end to end, said members having positive andnegative temperature co- 15 eicients of modulus of elasticityrespectivesaid elements being i such that the resultant eiectfof saidtemperature c 'Je i`1icients upon the vibrations of said member with'changes ofatmo'spheric tempcraturc'is positive, negativcvor zero, as'desired.

5. The methodof making] a tuning Ifork, which consists in forming eachvibratory member of 'a plurality of steel elements welded together ,endto end, said elements having positive and negative temperaturecoeflicients of modulus of elasticity respectively, and each of saidelements having a positive temperature coeicient of expansion, such thatthe resultant effect of the temperature coeicients of expansion andelasticity upon the vibratory member is substantially zero. l

In testimony whereof I ailix my signature.

HAKO'N` H.. HAGLUND.

